Mixture control for carburetors



June 14, 1955 c, SNYDER 2,710,604

MIXTURE CONTROL FOR CARBURETORS Filed Dec. 1, 1952 2 Sheets-Sheet 1 sY m m ATTORNEYS June 14, 1955 c. R. SNYDER 2,710,604

MIXTURE CONTROL FOR CARBURETORS 2 Sheets-Sheet 2 Filed Dec. 1, 1952 m' ZGM M ATTORNEY$ MEXTURE QZQNTROL FOR CARBURETORS Charles R. Snyder, Miami Beach, 'rla.

Application December 1, 1352, Serial No. 323,355

6 Claims. (Cl. 123-119) This invention relates to engine carburetors and, more particularly to carburetors of the type into which liquid fuels are introduced in metered quantities under valve regulated forced flow conditions, as distinguished from carburetors containing fuel-receiving float chambers from which fuel is led to aspirating jets for introduction into air streams passing through throttle-controlled passages leading to the engine cylinders.

In carburetors employing forced fuel delivery, the usual float chambers and float valve mechanisms of conventional carburetors are eliminated and the fuel is pumped in measured quantities directly into the mixing chamber of the carburetor for admixture with air drawn from the atmosphere, the volume of air so introduced being regulated by a movable throttle valve disposed in the air passage of the carburetor adjacent its air inlet. A forced flow carburetor without float-valve chambers has been disclosed in my prior Patent No. 2,595,721, granted May 6, 1952. While the carburetor of my aforesaid patent functions satisfactorily under normal conditions of motor vehicle engine operation, it does not provide for abnormal enrichment of the fuel mixture when the associated engine is first started. or when the same is operated when cold.

It is, therefore, one of the primary obgects of the invention to provide an improvement thereon by forming the said carburetor to include a mechanism for enriching the fuel mixtures produced by the carburetor for combustion in the cylinders of an associated engine when such an engine is initially operated, that is, before attaining its normal operating temperature, or when operated under low-temperature conditions.

While both manually and automatically operating choke devices are now and have been widely used in connection with conventional float-type carburetors to form fuel-enriched mixtures for facilitating engine starting and continued operation under low-temperature conditions, such prior devices embody throttle valve means for partially closing or choking the air inlet passages of the carburetors to increase negative pressures on the engine side thereof and thereby enable a larger quantity of liquid fuel to be aspirated from .the jet nozzles disposed in the air passages or mixing chambers of such conventional floattype carburetors. However, in the construction of the pressure fuel-delivery type of carburetor, in which the present invention is classifiable, wherein the fuel is delivered directly into the mixing chamber of the carburetor under pump-produced pressures, the ordinary choke mechanism of conventional carburetors cannot be used.

As disclosed in my prior patent, the fuel-metering valve of a pressure-fed fioatless carburetor is mounted for movement in a restricted passage through which liquid fuel is forced from a supply source, and under pump pressure, for delivery to the mixing chamber of the carburetor. The valve is spring-actuated in a manner to maintain the same normally in a position obstructing fuel flow through the passage. Actuating means are a eliorated June 14, 1955 provided, however, for .moving the valve against such spring pressure in a direction progressively decreasing the obstructions offered by the valve to fuel flow, the said actuating means, subject to movement thereof regulated by a manually operated control, being responsive to suction or negative pressures existing in the intake manifold of an associated engine, whereby to move said valve automatically between fuel flow-obstructing and admitting positions. Also, coupled with the movement of the fuel metering valve is an airflow-governing or throttle valve of the carburetor. This air valve normally functions in unison with the fuel-metering valve to cause the formation of carburetted fuel mixtures in volumes properly proportioned to meet various fuel demands and in a manner governed by the speed of the engine and the working loads imposed thereon.

With these features of carburetor operation and conrol, as found in my earlier patent, no provision exists for cold weather priming. Therefore, and in accordance with the present invention, I introduce into the carburetor a novel fuel-enriching or primer mechanism. By this mechanism, either through manual or automatic operation, the fuel-metering valve may have its operating positions adjusted so that it will provide for a relatively increased flow of fuel to the mixing chamber of the carburetor in quantities in excess of that which exist under normal operation.

Another primary object of the present invention is to provide means, responsive to the temperature of the walls of an engine with which the carburetor is joined, for adjusting the positions of a fuel metering valve of a carburetor having a forced pump-delivery of fuel thereto, whereby to admit of a limited but increased inflow of liquid fuel into a fuel carburetting or mixing passage of a carburetor when its associated engine is cold, as in starting the same, or prior to active operation thereof.

Another object of the invention is to provide an automatic priming or fuel-enriching means for such forced fuel-feeding carburetors, the means being so formed as to be rendered inactive when an associated engine is operating normally, but wherein said means, further,

are so formed as to respond automatically to predetermined low engine temperatures in a manner to increase the inflow of fuel therefrom to the engine throughout the entire operating range of the carburetor.

A further object is to provide a carburetor having a longitudinally slidable fuel-metering valve with which is combined an automatic choice or priming mechanism by which prompt engine-starting response on the part of. the carburetor is obtained under low-temperature operating conditions.

A further object is to provide a carburetor of the type in which conjoint operation of air and fuel-floW-controlling valves under manual regulation is effected by a pulsatory diaphragm, the latter being mounted in a casing in a manner dividing the casing internally so that on one side of the diaphragm a closed chamber is provided which communicates openly with the fuel-discharge passage of the carburetor, while on the opposite side of the diaphragm a second chamber is provided which cornmunicates openly with the atmosphere, whereby as the engine operates, unbalanced pressures are produced on opposite sides of the diaphragm and which are used to cause pulsation of the diaphragm in effecting controlled operation through opening and closing of the air and fuel flow valves.

A still further object is to provide a connection be tween the pulsatory diaphragm of such a carburetor and the shaft of its air-admitting throttle valve, said connection being such that pulsating movement of the diaphragm in one direction produces positively corresponding oscilto O latory movement of the throttle valve shaft, while movement of the diaphragm in an opposite direction serves, through a spring link forming a part of said connection, to produce either corresponding oscillatory movement of the valve shaft, or if the shaft should, through the actuation of other controls, be held against movement, said spring link will yield or expand, allowing normal movement of the diaphragm, but permitting the valve shaft to remain stationary until the restraining force thereon has been removed, after which its position in relation to the diaphragm will find normal restoration by the action of the spring.

For a further understanding of the invention, including additional objects, working principles and structural advantages, reference is to be had to the following description and the accompanying drawings, wherein:

Fig. 1 is a front elevational view of a carburetor formed in accordance with the present invention;

Fig. 2 is a rear elevational view thereof, parts of the mechanism being shown as broken away and in vertical cross section;

Fig. 3 is a vertical longitudinal sectional view taken through the carburetor on the plane indicated by the line 3-3 of Fig. 1;

Fig. 4 is a vertical sectional view showing a modified form of a manually operated valve mechanism for introducing a limited amount of liquid fuel to the mixing passage of my improved carburetor independently of the automatic throttle and fuel-metering valves thereof;

Fig. 5 is a similar view of the mechanism of Fig. 4, but disclosing an automatically controlled means for operating said fuel-admitting valve;

Fig. 6 is a vertical transverse sectional view taken on the line 6-6 of Fig. 3;

Fig. 7 is a detail horizontal sectional view, on the line 77 of Fig. 3, disclosing one of the cam projections of the priming means in a seated position in a socket therefor;

Fig. 8 is a detail front elevational view of a socket plate with which the projection-carrying cam plate of the priming mechanism cooperates;

Fig. 9 is a side view of the projection-providing priming plate and its actuating lever arm.

Fig. 10 is a detail sectional view on the line 1016 of Fig. 3;

Fig. 11 is a detail perspective view of one of the crank sleeves of the throttle valve shaft;

Fig. 12 is a similar view of the other cooperative sleeve on the throttle valve shaft.

Referring more particularly to the drawings, and to the form of my carburetor illustrated especially in Figs. 1 to 3, inclusive, the said carburetor comprises a casing which is designated in its entirety by the letter C. While the casing may be formed in different ways, in this instance the same has been shown as comprising a base section 10 and a superposed top section 11, the upper part of the base section 10 being flanged as at 12, which acts as a seat to receive a similar flange 13 formed on the bottom of the top section 11, the flanges 12 and 13 being preferably united by means of the removable fastening elements 14.

The top section 11 is provided with a main air-admitting open-ended passage 15. Located in this passage is an air flow-controlling or throttle valve 16, the same comprising advantageously a disk body 17 which is fixed to the center of a transversely extending mounting shaft 18, the latter being journaled for oscillation in bearing openings 19 formed in boss extensions 20 and 20a, which constitute a part of the top section 11.

One end of the shaft 18 projects beyond the extension 20 and has clamped thereto the hub 21 of a crank arm 22. Surrounding the hub extension 20 is a coil spring 23, one end 24 of which being secured to the casing of the top section 11, as shown in Fig. 4, while the other or free end of the spring is engaged with the outer end of the 4 crank arm 22, the arrangement and mounting of the spring 23 being such that its normal tendency when unopposed is to maintain the disk-like body 17 of the throttle valve in a position obstructing to its maximum extent air flow through the passage 15. It will be understood that air may enter the top of the passage 15 directly from the atmosphere or after being passed through a conventional dirt and dust-removing filter, not shown.

Such a position of the body of the throttle valve may be maintained by providing the opposite end of the shaft 18 which extends beyond the boss 29a with a crank member 25 having oppositely extending arms which carry at their outer ends adjustable screws 26, the latter being spaced for contact with a stationary web 27 forming a part of the top section 11, the spacing of the ends of the screws 26 thereby controlling the extent of oscillation of the shaft 18.

Beyond the boss 20a of the top section 11, the shaft 18 has fastened thereto the split hub of a sleeve 28. Loosely mounted for turning movement on the shaft 18, adjacent the hub 28 are the bifurcated collar-forming ends 30 of a diaphragm actuated crank 31. The outer end of this crank is connected with the radial arm 29 of the sleeve 28 by a coil spring shown in 32.

The outer end of the diaphragm crank 31 is pivotally united as at 33 to one end of a link 34, the opposite end of said link being joined at 35 to the central region of a pulsatory diaphragm 36, the latter being mounted centrally in a diaphragm casing 37. At one side of the diaphragm there is formed a suction chamber 37a, and lead ing from this chamber is a flexible pipe line 33. This line has its other end extended to the carburetor passage 15, entering the latter at a position below the throttle valve 16 and on the engine or intake manifold side of the carburetor, the pipe line being in direct communication with the air and fuel mixing chamber 39 of the carburetor which forms a continuation of the passage 15.

It will be noted that the diaphragm crank member 31 embodies a shoulder 39a which engages directly the under surface of the crank arm 29, so that with the parts in the position disclosed in Fig. 2 of the drawings, movement of the crank member 31 in a clockwise direction in response to diaphragm motion will produce corresponding movement on the part of the crank member 28. When the diaphragm 36 moves inwardly in response to high negative pressures in the fuel discharge side of the carburetor, the shoulder 39a moves away from the crank extension 29 of the sleeve 28. However, due to the inclusion of the yieldable link provided by the spring 32 movement of the crank member 29 in virtual unison with the crank member 31 will take place. This is true unless there should be some obstacle preventing rotation of the throttle shaft 18, as by a manual control hereinafter set forth. In that event, the spring 32 will yield and stretch, absorbing the motion of the diaphragm, but placing a positive force on the shaft 18 to rotate the same as soon as the restraining force preventing rotation of that shaft has been removed.

With the pistons of the associated engines in motion in their respective cylinders, atmospheric air is drawn into the carburetor through the passage 15. The air so admitted is admixed with finely divided liquid fuel so that the fuel may be drawn, as a vaporized combustible mixture, from the mixing chamber 39 and then to the engine cylinders.

When high vacuum or negative pressures exist in the chamber 39, the condition is transmitted to the diaphragm chamber 37a through the open pipe line 38, thereby unbalancing the pressures on opposite sides of the diaphragm 36, so that the diaphragm is flexed inwardly in response to the higher atmospheric pressures applied on its outer side. Movement is thereby imparted to the link 34 and the crank 31. Through the spring 32 corresponding movement is also imparted to the first crank 29 which, being clamped to the shaft 18, causes operation on the part of the throttle valve, unless the shaft is held against movement in its response to diaphragm flexing. if the shaft should be so held, it will be evident that the motion of the diaphragm will be absorbed by the stretching of the spring 32.

Adjacent to the boss extension and the crank arm 22, the shaft 18 carries another crank member 40. To the outer end of this member there is pivoted as at 41 the upper end of a connecting link 42, the lower end of said link being pivoted as at 43 on the outer end of a crank arm 44 which is pivotally mounted as at 45 on an intermediate portion of a crank arm 46. The hub 47 of the arm 46 is mounted for free turning movement on an outer surface of a sleeve member 43, which is stationarily supported in a socket 49 formed in the flange 12 of the base section 10.

The sleeve member 43 has slidably mounted therein a short tube section 50, the latter being formed with laterally projecting pins 51 (see Fig. 6) which are slidably received in slots 52 provided longitudinally in the sleeve member 48. The outer ends of the pins 51 engage with arcuate cam surfaces 53 provided on one side of the hub 47 of the crank arm 46, so that as the latter oscillates in response to movement imparted thereto by the crank member 40 and the link 42, longitudinal Sliding movement is imparted to the tube section 50.

This tube section receives the enlarged threaded end 54 of a needle valve 55, the end 54 being equipped with an adjustable stop nut 56, while the stem of the needle valve is formed intermediately of its length with a collar 57 with which engages one end of a coil spring 58, the other end of the last-named spring being engaged with an internal wall of the sleeve member 4%. The tapering forward end of the needle valve is arranged normally in the planes of intersection of a supplemental air passageway 5? and a liquid fuel-admitting passageway till, the latter being formed in a horizontally positioned tube 61 carried by the flange 12 and also in a transversely extending web member 62 disposed at the bottom of the main air passage 15 and clamped between the sections it; and 11.

A fuel delivering pipe line 63, which leads from any suitable source of liquid fuel supply, not shown, is connected with one end of the tube 61 by means of the detachable coupling nut 64. The supplemental air passage 59 is formed in connection with the walls of the top section 11 and air delivered to the upper end of the carburetor is by-passed in part through the passage 59, traveling around the throttle valve 16 in a confined flow stream and delivered to a vertical passage 65 in the web member 62, the passage 65 intersecting at right angles the liquid fuel passage 66 and continues by way of a discharge nipple 66 into the mixing chamber of the base section 10.

Thus, as the throttle valve 16 oscillates in response to fluid displacement effected by the reciprocating pistons of an associated engine, not shown, the movement of the throttle valve is imparted through the linkage described to the fuel flow controlling valve which, in the particular embodiment of my invention under consideration, assumes the form of the needle valve 55. As the throttle valve opens to more freely admit of air flow from the atmosphere through the passage 15, corresponding movement is imparted to the fuel valve in which the latter is caused to move outwardly, to the right as it is viewed in Fig. 3, thus further opening the passage 66 to provide for a proportionately increased flow of the liquid fuel.

This flow is further affected by the restricted air stream which travels through the passages 59 and 65 so that a finely divided body of liquid fuel is discharged from the nipple or nozzle 66 into the mixing chamber 39 of the base section 10. In the mixing chamber, the liquid fuel particles in a discrete form are admixed with the main body of air drawn from the atmosphere and pass through the passage 15. It will be understood that the member 62 comprises merely a web or spider and does not interfere to any particular extent with the main travel of air through the carburetor.

As above explained, the operation of the throttle valve depends upon the speed of the engine associated with the carburetor and the operating positions of the throttle valve are virtually automatically obtained so as to assure at all times properly proportioned delivery of carburetted fuel to the engine cylinders in accordance with the load conditions operatively imposed on the engine. However, manual regulation is present in the provision of a manually controlled adjustable stop 67 which is slidably mounted in one or more guides shown at 68 and is adapted to be connected with an accelerator pedal or other similar manual control, not shown, of a motor vehicle.

The stop member, conveniently, is in the form of a rod which slides in the guide or guides 68 and is urged forwardly by a coil spring 69 so that the stud '70 on the forward end of the rod will be arranged in the path of movement of the outer or lower end of the crank arm 46.

It will be seen that by manually actuating the stop member or rod 67 to slide the same against the resistance offered by the spring 69, the stud 70 may be removed from pyhslcal engagement with the outer end of the crank arm 46, as suggested by the spacing between these parts disclosed in Fig. 1 of the drawing.

As the engine increases in speed, the crank arm 46 swings toward the position of adjustment occupied by the stud 70 until it finally engages the stud, at which time further movement of the crank arm is prevented through such contact or engagement and the engine operated at the desired speed. if it should be desired that the speed be increased, the rod 67 is moved against the resistance of the spring 6% to again separate the stud 74 from the crank arm 46, allowing an additional increment of movement on the part of the crank arm 46 and the throttle valve 16. When retardation is desired, the vehicle operator releases the rod 67 either partially or fully so that the force of the spring 6? moves the crank arm 46 to desired positions to effect the necessary control of the throttle valve 16. In both acceleration and retardation of the engine, a uniformly carburetted mixture of liquid fuel and air is fed automatically to the cylinders of the engine in volumes proportionate to the speed of the engine and the working loads thereon. For instance, if the engine is laboring under a heavy load, as when a motor vehicle is ascending a steep hill or incline, the throttle valve remains automatically in but a partial open position in the passageway 15 and will remain in this position until the speed of the engine is increased as may be quickly accomplished by the vehicle operator in shifting to a lower gear ratio in the vehicle transmission.

in the conventional carburetor, the throttle valve moves to different positions through the operation of the accelerator pedal, which is manually performed. Thus when a motor vehicle is ascending a steep hill, the tendency for the operator is to push down on the accelerator and fully open the throttle valve, causing the formation of an overly rich fuel mixture and one improperly proportioned to obtain optimum operation under the conditions specified. In my improved carburetor, such a condition can not be obtained since the throttle valve is at all times under the control of the vacuum produced in the carburetor during the operation of the engine. The manual control provided by the stop 67 merely limits the opening movement of the throttle valve but it does not actually execute such opening movement, as that depends on engine operation.

It will be observed that the construction of the carburetor as above described is the same as that set forth in my aforesaid Patent 2,595,721, except for the lost motion provided for by the dual cranks indicated at 29 and 31. These cranks, with their connecting spring 32, are utilized in lieu of the single crank connection disclosed in my aforesaid prior patent to provide for improved diaphragm operation. Also, in the present construction, I utilize the relatively large diaphragm 35 for producing movement of the throttle valve in response to negative manifold pressures, rather than the small diametered piston and cylinder means employed for this purpose in the carburetor of my aforesaid patent, the diaphragm being preferred because of its greater surface area and its more positive and powerful response to unbalanced pressures on opposite sides thereof with respect to responses obtainable with a slidable piston arranged in a cylinder and adapted to be moved against friction forces established between the surfaces of the piston and the inner surfaces of the cylinder in which such a piston operates.

Another important improvement provided by the present invention in an automatic fuel-proportioning carburetor resides in the use of what I herein term for convenience in description an automatic fuel enriching or priming control. Such a control is desirable when the carburetor is being used under cold weather conditions or when an associated engine is to be initially started. The control is made possible by automatically adjusting the operating position of the needle type metering valve 55. In producing a limited flow of the liquid fuel from a source of supply into the chamber 39 of the carburetor through the nozzle 66, the priming control moves the valve 55 sufliciently so that the restricted fuel passage of the nozzle 66 is slightly uncovered to provide for direct inflow of liquid fuel into the carburetor when an associated engine is being started under low temperature conditions.

The initial opening of the valve member 55 is obtained by the provision of a cam disk shown at 75. This disk or ring is positioned on the sleeve member 48 between the hub 47 of the crank 46 and a flange washer 76, the latter being stationarily formed on the sleeve 48. The fiange washer 76 is formed with a plurality of depressions 78 in its outer face, which depressions are adapted to receive cam-shaped projections 79 provided on the disk or ring 75, the projections 79 being normally disposed in the depressions 78. The disk or ring 75 includes a depending crank extension 80, which is received in the forked outer end 81 of a crank arm 82.

The inner or hub end of the arm 82 is fixed to the outer or upper end of a shaft 83 rotatably supported in connection with a housing 84, the latter being mounted, as here shown, directly on the upper surface of an engine exhaust manifold 85, said manifold being arranged contiguous to an intake manifold shown at 86 and on which the fuel discharge throat of the carburetor is mounted. Connected with the shaft 83 is the inner end of a spiral thermostatic strip 87, the outer end of the strip being joined as at 88 with the stationary inner walls of the housing 84.

When the associated engine is cold, the thermostatic strip 37 responds to turn the shaft 83 connected therewith and the crank arm 82 in a direction causing the cam projections 79 to ride out of the depressions 78 of the ring 76. Longitudinal movement in an outward direction is thus imparted to the sleeve member 48 and the needle valve 54 carried thereby, withdrawing the pointed inner end of the metering valve from its normal position closing the nozzle bore 66. This retraction of the needle valve is sufiicient to provide for the enriched inflow of liquid fuel into the mixing chamber of the carburetor in response to pump pressures and the move ment of the engine pistons, producing a rich mixture adapted for ready vaporization and ignition. When the engine obtains normal operating temperatures, the heat of the exhaust manifold is transmitted to the thermostatic strip 87 and the housing 84, causing the latter to rotate the shaft 83 and the crank member 82 in. a direction opposite to that previously described, so that the cam projection 79 will be restored to registry with the depression 78, thereby bringing the valve 55 into its normal operating relationship with the nozzle 66.

As shown in Fig. 9 the depending end of the crank extension may be joined with a manually operating link 89, whereby to adjust the disk 75 rotatably on the sleeve member 48, rather than to rely on the automatic control provided by the thermostatic strip 87. Either construction may be used, as desired.

Another modification has been disclosed in Fig. 4, where the priming operation is obtained by a valve 90, the casing of which is threaded, as at 91, into an opening formed in the wall of the carburetor C below its throttle valve. The valve 90 includes a central bore 92 into which leads a fuel passage shown at 93. Normally this passage is closed by a spring pressed valve member 94, which is used in the priming operation in place of the needle valve 55 of Fig. 3. The operating stem 95 of this valve member projects exteriorly of the valve and is pivotally connected with one arm of a bell crank lever 96, the central part of said lever being pivotally mounted as at 97 on the casing of the valve 90. Also, the bell crank lever may be connected with a manually operated rod 98, by which said bell crank lever may be operated in a manner elevating the valve member 94 and unseating the same to permit of the flow of fuel through the passage 93 and then into a passage 99 leading to the interior of the carburetor C. Air may be admixed with this fuel so admitted by way of the air inlet passage indicated at 100. As shown in Fig. 5, the valve member 94 may be actuated by a thermostatic strip 87 in an automatic manner, rather than by use of the manual control 98.

In view of the foregoing it will be seen that my present invention improves carburetors of the type set forth in my aforesaid patent by providing a priming or enriching means therefor which adapts the carburetor to the ready starting of cold engines or to low temperature conditions generally. The enriching or priming mechanism may be readily applied to the carburetor and adds very little, because of its structural simplicity or cost. Another improvement provided by the present invention is the diaphragm control by which operation of the throttle valve shaft 18 is automatically effected. These improvements contribute substantially to a generally improved operation as well as the utility of a carburetor of the type set forth.

I claim:

1. in a carburetor for internal combustion engines, a casing formed with an internal passageway, a throttle valve positioned in said passageway for movement therein between positions substantially obstructing and unobstructing air fiow therethrough, means responsive to intake manifold pressures developed by the operation of an associated engine in producing partial vacuum conditions in said passageway for moving said valve automati- Cally between its positions obstructing and unobstructing the passageway to air flow, said last-named means embodying a movable displacement member, motion transmitting means uniting said member with said throttle valve to effect movement of the latter in proportion to the degree of movement of the displacement member, spring means opposing the action of said displacement member, means for introducing a vaporizable liquid fuel in said passageway, said last-named means including a movable fuel-metering valve, means linking said throttle and fuel-metering valves for movement in unison, a

manually controlled stop device regulating the extent of movement of said valves in response to operating forces produced thereon by said manifold pressure means, and thermostatic means responsive to the temperature of the associated engine for effecting automatically an initial opening movement of said metering valve to admit of fuel flow into said passageway independently of movement imparted to said metering valve by said manifold pressure responsive means.

2. A carburetor comprising a casing, the latter being formed with an internal chamber having an air inlet and a carburetted fuel outlet; a rock shaft journaled in the walls of said casing; a movable air-flow controlling valve mounted in said chamber on said shaft adjacent to the air inlet; a liquid fuel supplying means entering said chamber between said valve and said outlet; a movable metering valve controlling the flow of fuel through said supply means to said chamber; an oscillatory crank arm mounted on one end of said rock shaft; an oscillatory crank arm for actuating said fuel-metering valve; means directly linking the outer ends of said crank arm to effect substantially synchronous movement of said valves, automatic means including a cylinder and diaphragm assembly responsive to predetermined engine manifold pressures developed in said chamber for actuating said valves; a manually operated stop member cooperative with said valves to arrest variably their opening response to the automatic operation of said manifold pressure means; spring means cooperative with said valves for counteracting forces exercised thereon by said cylinder and diaphragm assembly in moving the valves toward their positions of closure when said stop member is released, and thermostatic means responsive to the temperature of the associated engine for effecting an initial opening of said metering valve in admitting of fuel flow into said passageway independently of the movement imparted to said metering valve by said manifold pressure responsive means.

3. In a carburetor for internal combustion engines; a casing formed with an internal passageway, one end of said passageway constituting an air inlet and being disposed in communication with the atmosphere, the other end of said passageway constituting a carbureted fuel outlet adapted for communication with the cylinders of an associated engine; a throttle valve positioned in said passageway adjacent the air inlet end thereof; a liquid fuel-supplying means entering said passageway between said valve and the outlet thereof; a movable metering valve controlling the flow of fuel to said supply means to the passageway; means responsive to engine manifold pressures produced in said passageway for imparting synchronized operation to said throttle and metering valves, and means responsive to the temperature of the associated engine for partially opening said metering valve to produce a limited inflow of liquid fuel into said passageway independently of the operation of said metering valve effected through said manifold pressure responsive means.

4. In a carburetor; a casing formed with a passageway communicating at one end with the atmosphere metering valve to provide for limited opening movement thereof in admitting of fuel flow into said passageway independently of said manifold pressure responsive means. i

5. In a carburetor; a casing formed with a passageway communicating at one end with the atmosphere and at the other end thereof with the cylinders of an associated engine; conduit means for the advancement of liquid fuel under forced flow directly to said passageway; a movable metering valve positioned in said con duit means governing the flow of fuel passing therethrough into said passageway; means responsive to engine manifold pressures existing in the outlet of said carburetor for controlling opening and closing movements of said metering valve; and thermally responsive means mounted on the associated engine and operatively coupled with said metering valve to produce limited opening movement thereof in admitting fuel flow into said passageway upon the presence of predetermined operating temperatures on the part of said engine.

6. In a carburetor for internal combustion engines; a casing formed with an internal passageway, one end of the latter communicating with the atmosphere and the other end thereof with the cylinders of an associ ated engine; a movable throttle valve positioned in said passageway contiguous to its air inlet end; a liquid fuel supplying means entering said passageway between said valve and the outlet of said passageway leading to the engine, said fuel-supplying means embodying a tube of restricted cross-sectional area extending transversely across said passageway and formed intermediately of its length with a lateral outlet conduit opening into said passageway; a needle valve slidably mounted in said tube to regulate the flow of fluid through the tube and outlet conduit, said needle valve including a stem extending to the exterior of said casing; spring means cooperative with said stem normally serving to maintain the needle valve in a position substantially arresting liquid fuel flow through said conduit and into said passageway; means carried by the exteriorly extending portion of said needle valve for moving the latter to a position providing for fuel flow into said passageway upon the presence of predetermined engine manifold pressures in the outlet of said passageway; and thermally actuated means mounted in connection with said engine and coupled with said metering valve to cause the latter to move to a partially opened position in admitting of fuel flow into said passageway when predetermined relatively low operating temperatures prevail around said engine.

References Cited in the file of this patent UNITED STATES PATENTS 1,544,306 Franzen June 30, 1925 1,544,748 Haskins et al July 7, 1925 2,092,297 Allen Sept. 7, 1937 2,408,104 Stanton Sept. 24, 1946 2,457,570 Leibing Dec. 28, 1948 2,583,406 Arnold Ian. 22, 1952 2,595,721 Snyder May 6, 1952 

